Lumiline Linear Incandescent Lamp
Although double-ended lamps existed since the 1890s, they only became popular after Alfred Beuttell's 1901 invention of the 'Linolite' lamp. Those were made according to standard lampmaking methods with a glass-to-wire seal at each end of the tube. This introduced a dead-space beyond which the filament could not extend, frustrating attempts to create continuous lines of light. In 1932 German Osram introduced its improved 'Linestra' lamp, with the glass-to-metal seals being brought out through the tube sides. This allowed the filament to be extended right to the ends, but the cost is rather high due to the more complex manufacturing.

In 1934 GE launched this 'Lumiline' lamp, developed by Paul O. Cartun. The filament extends almost to the ends via a much simpler lamp design. Instead of sealing metal wires through the glass, the ends are closed by a pair of metallic discs. These are made of 'Allegheny 55' alloy consisting of 29% chromium in iron, whose thermal expansion coefficient matches the soda-lime glass bulb. The discs are cup-shaped for high strength. They each bear a central depression, which mates with a pair of low profile snap-on annular spring terminals which mount the lamps into their holders.

One of the discs has a small hole at its centre, through which a small diameter glass tube is fused - this is used to exhaust the lamp, before being sealed off. The filament is supported by fine molybdenum wires, carried by small glass beads fused into a U-shaped metal spine. One end is welded to one disc, and the other makes contact via a sprung wire. The first Lumiline lamps were introduced in 15W and 30W ratings of 18" length. A high brightness 40W 12" lamp later appeared, followed finally by this 60W 18" model.
Manufacturer: General Electric U.S.A.
Lamp Power: 60 Watts
Lamp Voltage: 120 Volts
Lamp Current: 0.5 Amperes
Cap Type: Disc Allegheny 55 alloy
Bulb Type: T-26 T-8 in eighths/inch
Bulb Finish: Clear Soda-lime glass
Filament Type: C-8 Single coil
Atmosphere: Vacuum Red phosphorus getter
Luminous Flux: 565 lm
Luminous Efficacy: 9.4 lm/W
Beam Intensity: N/A
Beam Distribution: N/A
Colour Temperature & CRI: CCT: 2400K CRI: Ra 100
Chromaticity Co-ordinates: CCx: 0.486 CCy: 0.415
Rated Lifetime: 1500 hours
Burning Position: Universal
Overall Length: 451 mm 17 3/4 inches
Lighted Length: 425 mm 16 3/4 inches inches
Factory: Mattoon, IL U.S.A.
Date of Manufacture: 1958
Original Value: US $2.35 1961
 
References: 1) GE Large Lamp Catalogue, USA, 1956, p.26
2) GE Large Lamp Price Schedule, Form 2195, 29th March 1961, p.10.
3) Lamps for a Brighter America, P.W.Keating, publ. McGraw-Hill 1954, p.159
4) US Patent 2,032,791 - Tubular and Other Incandescent Lamps and their Manufacture - Paul O. Cartun - General Electric USA - Filed 20th April 1933.